Motor gasoline composition

ABSTRACT

An embodiment of the present invention provides a motor gasoline composition which controls formation of deposits in air intake systems and combustion chambers (particularly, the latter) of gasoline engines, keeping them clean without using a detergent.  
     The motor gasoline composition contains saturated hydrocarbons, aromatic hydrocarbons having a carbon number of 7 or less, and aromatic hydrocarbons having a carbon number of 8 or more, the composition having a combustion chamber deposit formation controlling index satisfying the following relationship:  
     Combustion chamber deposit formation controlling index A/B&gt;6 wherein, A is a total content (wt. %) of saturated hydrocarbons of unspecified carbon number and aromatic hydrocarbons having a carbon number of 7 or less, and B is a total content (wt. %) of aromatic hydrocarbons having a carbon number of 8 or more.

FIELD OF THE INVENTION

[0001] This invention relates to a motor gasoline composition, more particularly the composition showing excellent effects of cleaning gasoline engine combustion chambers.

BACKGROUND OF THE INVENTION

[0002] It is known that a fuel oil, e.g., gasoline, for internal combustion engines tends to form sludge and deposits (hereinafter referred to simply as deposits) in an air intake system and combustion chamber. Deposits formed on an air intake system prevent smooth flow of air and fuel oil into the combustion chamber, possibly causing deteriorated engine output power, operability or exhaust gas performance. Deposits formed in a combustion chamber increase required engine compression ratio or gasoline octane number, and cause various problems, e.g., deteriorated engine output power, operability or exhaust gas properties, and production of noise in the chamber. Therefore, it has been strongly demanded to control formation of deposits both in an air intake system and combustion chamber, thereby keeping them clean. More recently, gasoline engines have been notably more functional, and hence more sensitive to these deposits.

[0003] For example, an electronically controlled fuel injection device precisely controls air/fuel ratio, improves engine performance, and also effectively saves energy and improves exhaust gas performance. However, when deposits are formed in the air intake valve, the gasoline droplets injected from the device contact the deposits, making it difficult to precisely control air/fuel ratio, adversely affecting engine operability. The direct-injection type gasoline engine, attracting much attention recently for its high energy-saving effect, is free of problems resulting from deposits formed in the air intake system, because it directly injects fuel in the cylinder. Nevertheless, however, it cannot be freed from the problems caused by deposits formed in the combustion chamber, because they may increase required engine compression ratio or gasoline octane number, as described earlier, disturb air flow in the combustion chamber, and adversely affect combustibility of gasoline in a superlean burning condition, hindering not only superhigh fuel efficiency as its major advantage but also exhaust gas performance.

[0004] Japanese Laid-open Patent Application No.55-25489, and Japanese Patent Publication Nos.55-39278, 56-48556 and 61-33016 disclose motor gasoline incorporated with a polyetheramine-based compound as the additive, to improve cleanability of air intake valves and ports of gasoline engines. Japanese Laid-open Patent Application No.2-261806 discloses a polyisobuteneamine-based compound as the additive for the same purposes. However, these additives, while improving cleanability of air intake systems of gasoline engines, show essentially no effect for cleaning combustion chambers, frequently having an adverse effect. Japanese Laid-open Patent Application No.4-88091 discloses an additive composition comprising a polyoxyalkylene glycol (molecular weight: 500 to 5,000) or its derivative, alkylamine and lubricant fraction for gasoline, describing that gasoline incorporated with the additive controls formation of deposits on engine air intake systems. However, gasoline incorporated with a lubricant fraction will deteriorate cleanability of engine combustion chambers. Japanese Laid-open Patent Application No.3-229797 discloses a polyetheramine-based compound as the additive, describing that gasoline incorporated with the additive improves cleanability of both air intake systems and combustion chambers of gasoline engines.

[0005] These techniques, however, inevitably increase motor gasoline cost, because of incorporation of additives, and their effects of improving cleanability of air intake systems and combustion chambers (particularly, the latter) are still insufficient.

SUMMARY OF THE INVENTION

[0006] Preferred embodiments include:

[0007] 1. A motor gasoline composition containing saturated hydrocarbons, aromatic hydrocarbons having a carbon number of 7 or less, and aromatic hydrocarbons having a carbon number of 8 or more, said composition having a combustion chamber deposit formation controlling index satisfying the following relationship:

[0008] Combustion chamber deposit formation controlling index =A/B>6 wherein, A is a total content (wt. %) of saturated hydrocarbons of unspecified carbon number and aromatic hydrocarbons having a carbon number of 7 or less, and B is a total content (wt. %) of aromatic hydrocarbons having a carbon number of 8 or more.

[0009] 2. A method of controlling combustion chamber deposits by providing to an internal combustion engine an effective deposit controlling amount of the composition of claim 1.

BRIEF DESCRIPTION OF THE DRAWING

[0010] The Figure shows the relationship between relative quantity of combustion chamber deposits formed and combustion chamber deposit formation controlling index.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] An embodiment of the present invention to provide a motor gasoline composition which controls formation of deposits in air intake systems and combustion chambers (particularly, the latter) of gasoline engines, keeping them clean without using a detergent.

[0012] The inventors invention have found that formation of deposits in air intake systems and combustion chambers of gasoline engines is controlled when gasoline satisfies a specific relationship between total content of saturated hydrocarbons and aromatic hydrocarbons having a carbon number of 7 or less and total content of aromatic hydrocarbons having a carbon number of 8 or more, reaching the present invention.

[0013] An embodiment of the present invention provides the motor gasoline composition containing saturated hydrocarbons, aromatic hydrocarbons having a carbon number of 7 or less, and aromatic hydrocarbons having a carbon number of 8 or more, the composition having a combustion chamber deposit formation controlling index satisfying the following relationship:

[0014] Combustion chamber deposit formation controlling index=A/B>6 wherein, A is a total content (wt. %) of saturated hydrocarbons of unspecified carbon number and aromatic hydrocarbons having a carbon number of 7 or less, and B is a total content (wt. %) of aromatic hydrocarbons having a carbon number of 8 or more.

[0015] An embodiment of the present invention relates to the above-described motor gasoline composition, and the preferred embodiments include:

[0016] 1. a motor gasoline composition having a combustion chamber deposit formation controlling index of 8.5 or more, and

[0017] 2. the motor gasoline composition above described or according to (1), wherein it is unleaded.

[0018] Preferred embodiments of the present invention are described more concretely, below. The motor gasoline of the present invention has a combustion chamber deposit formation controlling index above a specific value, wherein the index is determined by a total content of saturated hydrocarbons and aromatic hydrocarbons having a carbon number of 7 or less, and total content of aromatic hydrocarbons having a carbon number of 8 or more.

[0019] 1. Combustion Chamber Deposit Formation Controlling Index

[0020] In this specification, combustion chamber deposit formation controlling index is defined by the following relationship:

[0021] Combustion chamber deposit formation controlling index=A/B>6 wherein, A is a total content (wt. %, based on the whole motor gasoline composition) of saturated hydrocarbons of unspecified carbon number and aromatic hydrocarbons having a carbon number of 7 or less, and B (wt. %, based on the whole motor gasoline composition) is a total content of aromatic hydrocarbons having a carbon number of 8 or more.

[0022] The method for determining content of saturated hydrocarbons, aromatic hydrocarbons having a carbon number of 7 or less, or aromatic hydrocarbons having a carbon number of 8 or more is not limited. They can be determined by analyzing total hydrocarbon components present in the gasoline composition by known methods. For example, they are normally determined by programmed-temperature capillary gas chromatography.

[0023]FIG. 1 shows the relationship between relative quantity of deposits formed in a combustion chamber and combustion chamber deposit formation controlling index, wherein the line 1 represents the relationship between them and inflection point 2 is at a combustion chamber deposit formation controlling index of 6 representing the relationship between relative quantity of deposits formed in a combustion chamber and combustion chamber deposit formation controlling index. Diamonds refer to Engine A, squares to Engine B and triangles to Engine C. As shown, quantity of deposits formed in a combustion chamber decreases as combustion chamber deposit formation controlling index increases up to 6, at which the quantity attains a minimum and becomes constant thereafter with the index. FIG. 1, showing the relationship between relative quantity of deposits formed in a combustion chamber and combustion chamber deposit formation controlling index, relates to an index of controlled formation of deposits in combustion chambers of gasoline engines, for the reasons described later, and represents tendency of deposit formation in a combustion chambers.

[0024] Tendency of deposit formation in a combustion chamber can be known by comparing absolute quantities of deposits formed by operating the same engine under the same conditions. It can be also known by comparing the absolute quantity with the one observed when a clean motor gasoline which causes no formation of deposits to a significant extent is used. In this case, the tendency is given by a relative value, with the quantity of deposits formed with the clean gasoline serving as the standard (1.0).

[0025] The relative quantity can represent tendency of deposit formation in a combustion chamber, irrespective of engine type used. FIG. 1 plots relative quantities of deposits formed in combustion chambers of 3 different engine types against combustion chamber deposit formation controlling index, representing tendency of deposit formation in combustion chambers for motor gasoline.

[0026] 1. Motor Gasoline Composition

[0027] The motor gasoline composition is mainly composed of a mineral oil and has a combustion chamber deposit formation controlling index above 6, preferably 7 or more, more preferably 8.5 or more. Decreasing combustion chamber deposit formation controlling index to 6 or less will be accompanied by increased quantity of deposits formed in an air intake system and combustion chamber (particularly, the latter). The upper limit of the index is not limited, but normally in a range from 90 to 150, in consideration of required gasoline properties and gasoline production cost.

[0028] The mineral oil as the major component for the motor gasoline is a petroleum fraction having a 10% distillation point of 70° C. or lower, 97% distillation point of 205° C. or lower, and existent gum content of 5 mg/100 ml or less. It may be a straight-run petroleum fraction produced by atmospheric distillation of various types of crudes (e.g., paraffin-base, naphthene-base, mixed-base, special crude, and a mixture thereof), or produced by a combination of hydrocracking, catalytic cracking, catalytic reforming or the like which refines a heavy petroleum fraction. These fractions may be used either individually or in combination. The other components useful for the present invention include light fractions derived from oil shale, oil sand and coal, and those produced by synthesis from methanol.

[0029] The combustion chamber deposit formation controlling index can be kept in the specific range by adequately blending various types of base gasoline stocks of different hydrocarbon compositions, when a motor gasoline composition is produced by blending light petroleum fractions other than the above-described petroleum or mineral oil fractions. The gasoline base stocks of different hydrocarbon compositions and useful for the present invention include hydrocarbons abundant in saturates (e.g., straight-run naphtha and alkylate); those abundant in aromatics having a carbon number of 7 or less (e.g., benzene, benzene fraction, toluene, toluene fraction and light reformate); and those abundant in aromatics having a carbon number of 8 or more (e.g., ethylbenzene, ethylbenzene fraction, xylene, xylene fraction, heavy reformate and heavy cracked naphtha).

[0030] The motor gasoline composition, having the characteristics described above, satisfies No. 1 or No.2 gasoline as specified by JIS K2202, which corresponds to premium or regular motor gasoline, respectively, and includes reformate-based, crackate-based, low-lead or unleaded motor gasoline.

[0031] The motor gasoline composition may be incorporated with a known detergent, as required to further control formation of deposits in air-intake systems and combustion chambers, so long as its required properties are not damaged. The detergents useful for the present invention include a polyetheramine-based compound, hydroxylamine-based compound, and polyoxyalkylene glycol. Content of the detergent is not limited, but normally in a range from 0.001 to 5 wt. %, based on the whole gasoline composition.

[0032] The polyetheramine-based compounds useful for the present invention include those shown by general formula (1):

R—O(AO)m—(C₃H₆NH)n—H  (1)

[0033] wherein, R is a hydrocarbon residue having a carbon number of 10 to 50, A is an alkylene group having a carbon number of 2 to 6, (m) is an integer of 1 to 3, and (n) is an integer of 10 to 50.

[0034] The hydroxylamine-based compounds useful for the present invention include those shown by general formula (2):

[0035] wherein, R is methylene group or an alkylene group having a carbon number of 2 to 3; A¹, A², A³ and A⁴ are each an alkylene group having a carbon number of 2 to 4, at least one of Al to A⁴ containing propylene group; and (m), (n), (p) and (q) are each a positive integer, satisfying the relationship (m+n+p+q) is 4 to 200.

[0036] The polyoxyalkylene glycol compounds useful for the present invention include those shown by general formula (3) and containing, as the major component, the polyoxyalkylene glycol of 500 to 5,000 in average molecular weight:

O—(AO)n—H  (3)

[0037] wherein, A is a mixed alkylene group of ethylene and propylene groups, and (n) is a positive integer. It is preferable that content of the oxypropylene group in the polyoxyalkylene glycol is 50 wt. % or more, based on the whole polyoxyalkylene glycol.

[0038] The motor gasoline composition may be also incorporated with another known additive for fuel oil, so long as its properties are not damaged. Suitable additives include a surface ignition inhibitor, e.g., tricresyl phosphate (TCP) and trimethyl phosphate; metal deactivator represented by salicylidene derivative, e.g., N,N′-salicylidenediaminopropane; de-icer, e.g., alcohol and succinimide; corrosion inhibitor, e.g., aliphatic amine salt, sulfonate and alkylamine phosphate; anti-static agent, e.g., anionic, cationic and ampholytic surfactants; colorant, e.g., azo-based dye; and anti-oxidant represented by phenol (e.g., 2,6-di-tert-butyl-p-cresol) and aromatic amine (e.g., phenyl-α-naphthylamine). These additives may be used either individually or in combination. Content of the additive is not limited, but is normally 0.5 wt. % or less, based on the whole gasoline composition.

[0039] The motor gasoline composition may be also incorporated with an oxygenated compound, so long as its properties are not damaged. The oxygenated compounds useful for the present invention include methanol, ethanol, methyl-tert-butyl ether, and ethyl-tert-butyl ether. Content of the oxygenated compound is not limited, but is normally 0.1 to 10%, based on the whole gasoline composition.

EXAMPLES

[0040] Preferred embodiments of the present invention are described further in detail by EXAMPLES and COMPARATIVE EXAMPLES, which do not limit the present invention. Test Gasoline compositions used for EXAMPLES and COMPARATIVE EXAMPLES comprised gasoline stocks produced by the normal methods, and adequately blended. They were different from each other in hydrocarbon composition (saturated hydrocarbons, aromatic hydrocarbons having a carbon number of 7 or less, and aromatic hydrocarbons having a carbon number of 8 or more), and hence in combustion chamber deposit formation controlling index.

[0041] Table 1 shows properties of Test Gasoline compositions used for EXAMPLES 1 to 4. TABLE 1 Test Gasoline compositions (1) (2) (3) (4) Specific gravity, g/cm³ (15° C.) 0.739 0.750 0.735 0.723 Distillation, ° C. Initial boiling point 47.5 34.0 30.5 30.5 10% 73.5 47.0 54.0 52.0 50% 105.0 80.0 91.5 92.0 90% 137.0 149.0 121.0 158.5 End point 177.0 176.0 175.5 192.5 RON 100 100 92 92 Hydrocarbon composition, wt. % A [saturated hydrocarbons and 99 82 92 77 aromatic hydrocarbons having a carbon number of 7 or less (C ≦ 7) B [aromatic hydrocarbons having a 1 1.3 1.9 9.2 carbon number of 8 or more (C ≧ 8) RVP kPa 46.09 50.99 67.66 68.64

[0042] The hydrocarbon composition of each Test Gasoline was determined by capillary gas chromatography. Table 2 describes the analyzer and test conditions. TABLE 2 Analyzer Gas chromatograph Shimadzu's GC-14B Detector Flame ionization detector Column Capillary column (0.2 mm in diameter, 50 m long), Stationary liquid (crosslinked methyl silicon) Split type (split ratio: 1/50) Sample injector Test conditions Column temperature heated to 5 to 200° C. (at 2° C./min, 5° C./min) Carrier gas flow rate 1 ml/min (nitrogen gas) Sample quantity 0.2 μl Sample injector temperature 250° C.

Example 1

[0043] The cleanability test was carried out for Test Gasoline (1) shown in Table 1, using the test engine A.

COMPARATIVE EXAMPLES 1 to 3

[0044] The cleanability test was carried out for Test Gasoline (1 a), (1 b) and (1 c) shown in Table 3, using the test engine A.

[0045] Table 3 shows Test Gasoline properties and the cleanability test results. Quantity of deposits observed in each run was relative to the one observed in EXAMPLE 1 which used Test Gasoline (1), where quantity of the deposits was taken as unity (1.0).

[0046] Test Gasoline (1 a), (1 b) and (1 c) compositions used for COMPARATIVE EXAMPLES 1 to 3 comprised gasoline stocks produced by the normal methods and adequately blended, as was the case with Test Gasoline (1) for EXAMPLE 1. They were different from each other in hydrocarbon composition (saturated hydrocarbons, aromatic hydrocarbons having a carbon number of 7 or less, and aromatic hydrocarbons having a carbon number of 8 or more), and hence in combustion chamber deposit formation controlling index. TABLE 3 Test Engine A COMPARATIVE EXAMPLE EXAMPLES 1 1 2 3 Test Gasoline types (1) (1a) (1b) (1c) Test Gasoline properties Hydrocarbon composition, wt. % A [saturated hydrocarbons and 99 72 61 43 aromatic hydrocarbons having a carbon number of 7 or less (C ≦ 7) B [aromatic hydrocarbons having a 1 12 23 45 carbon number of 8 or more (C ≧ 8) RON Combustion chamber deposit 100 90 90 97 formation controlling index 99 6.0 2.7 1.0 Cleanability test results Quantity of deposits formed in the 1.0 1.2 1.7 3.1 combustion chamber*

[0047] Each gasoline cleanability test run was carried out in accordance with JASO M352-98 continuously for 50 hours, using the test engine A described in Table 4, on the operational modes I and II shown in Table 5. On completion of the test, the engine was disassembled, to scour off the deposits from the combustion chamber and measure the weight. Cleanability of each Test Gasoline was evaluated by weight of the deposits formed in the combustion chamber. TABLE 4 Test Engine A B C Valve mechanism 4-valve/DOHC 2-valve/OHC 4-valve/DOHC Fuel injection mode PFI PFI DI Number of cylinders 6 cylinders in 1 cylinder 4 cylinders in series 1988 series 1998 Total displacement, ml 9.6 244 10.0 Compression ratio  135/5600 10.0 145/6000 Max. Power output, 18.0/4800  20/7000  20/4400 ps/rpm Max. Torque, kg-cm/rpm 2.2/5500

[0048] TABLE 5 Operational modes Operational conditions I II Speed, km/hour 40 70 Operational time, hours 25 25 Load, W RL RL Cooling water temperature, ° C. 90 90

Example 2

[0049] The cleanability test was carried out for Test Gasoline (2) shown in Table 1, using the test engine B.

Comparative Examples 4 to 6

[0050] The cleanability test was carried out for Test Gasoline (2 a), (2 b) and (2 c) shown in Table 6, using the test engine B.

[0051] Table 6 shows Test Gasoline properties and the cleanability test results. Test Gasoline (2 a), (2 b) and (2 c) compositions used for COMPARATIVE EXAMPLES 4 to 6 comprised gasoline stocks produced by the normal methods and adequately blended, as were the cases with Test Gasoline (1 a), (1 b) and (1 c) compositions. TABLE 6 Test Engine B COMPARATIVE EXAMPLE EXAMPLES 2 4 5 6 Test Gasoline types (2) (2a) (2b) (2c) Test Gasoline types Test Gasoline properties Hydrocarbon composition, wt. % A [saturated hydrocarbons and 82   74   70   65   aromatic hydrocarbons having a carbon number of 7 or less (C ≦ 7) B [aromatic hydrocarbons having a 1.3 13   20   26   carbon number of 8 or more (C ≧ 8) RON 96   96   96   96   Combustion chamber deposit 63.1  5.7 3.5 2.5 formation controlling index Cleanability test results Quantity of deposits formed in the 1.0 1.3 1.3 1.6 combustion chamber*

Examples 3 and 4

[0052] The cleanability test was carried out for Test Gasoline (3) for EXAMPLE 3 and Test Gasoline (4) for EXAMPLE 4, each shown in Table 1, using the test engine C.

Comparative Examples 7 to 9

[0053] The cleanability test was carried out for Test Gasoline (3 a), (3 b) and (3 c) shown in Table 7, using the test engine C.

[0054] Table 7 shows Test Gasoline properties and the cleanability test results. Test Gasoline (3 a), (3 b) and (3 c) compositions used for COMPARATIVE EXAMPLES 7 to 9 comprised gasoline stocks produced by the normal methods and adequately blended, as were the cases with Test Gasoline (1 a), (1 b) and (1 c) compositions. TABLE 7 Test Engine C COMPARATIVE EXAMPLE EXAMPLES 3 4 7 8 9 Test Gasoline types (3) (4) (3a) (3b) (3c) Test Gasoline properties Hydrocarbon composition, wt. % A [saturated hydrocarbons 92 77 81 65 55 and aromatic hydrocarbons having a carbon number of 7 or less (C ≦ 7) B [aromatic hydrocarbons 1.9 9.2 17 26 39 having a carbon number of 8 or more (C ≧ 8) RON Combustion chamber 92 92 92 92 97 deposit formation 48.4 8.4 4.8 2.5 1.4 controlling index Cleanability test results Quantity of deposits formed 1.0 0.9 1.4 2.0 2.3 in the combustion chamber *

[0055] The cleanability test results, shown in Table 3, indicate that quantity of the deposits formed in the combustion chamber of the commercial Test Engine A in EXAMPLE 1 was much smaller than those formed in COMPARATIVE EXAMPLES 1 to 3, which used Test Gasoline compositions having a combustion chamber deposit formation controlling index of 6 or less. The similar results are observed in the cleanability tests using the test engine B (Table 6): quantity of the deposits formed in the combustion chamber in EXAMPLE 2 was much smaller than those formed in COMPARATIVE EXAMPLES 4 to 6. The similar results are also observed in the cleanability tests using the direct-injection type test engine C (Table 7): quantities of the deposits formed in the combustion chambers in EXAMPLES 3 and 4 were much smaller than those formed in COMPARATIVE EXAMPLES 7 to 9.

[0056] As described above, the motor gasoline composition provides enhanced effects of controlling formation of deposits in air intake systems and combustion chambers (particularly, the latter) of gasoline engines, to keep the combustion chambers clean by satisfying a specific relationship between total content of saturated hydrocarbons and aromatic hydrocarbons having a carbon number of 7 or less and total content of aromatic hydrocarbons having a carbon number of 8 or more. 

What is claimed is:
 1. A motor gasoline composition containing saturated hydrocarbons, aromatic hydrocarbons having a carbon number of 7 or less, and aromatic hydrocarbons having a carbon number of 8 or more, said composition having a combustion chamber deposit formation controlling index satisfying the following relationship: Combustion chamber deposit formation controlling index=A/B>6 wherein, A is a total content (wt. %) of saturated hydrocarbons of unspecified carbon number and aromatic hydrocarbons having a carbon number of 7 or less, and B is a total content (wt. %) of aromatic hydrocarbons having a carbon number of 8 or more.
 2. A method of controlling combustion chamber deposits by providing to an internal combustion engine an effective deposit controlling amount of the composition of claim
 1. 